PROEJECT SUMMARY Pre-exposure prophylaxis (PrEP) with emtricitibine/tenofovir disoproxyl fumarate (FTC/TDF) has been shown to dramatically reduce transmission of HIV in men who have sex with men (MSM). However, as an antiretroviral medication, it does not protect against other sexually transmitted infections (STIs). Currently in the US, STI rates are at an ?unprecedented high,? according to the Centers for Disease Control and Prevention. These elevated rates are especially pronounced in MSM prescribed PrEP and represent a crucial public health problem that requires immediate attention. Dr. Clement's K23 proposal will focus on addressing this problem through the use of mobile health (mHealth) technology in a critically important population with profound health disparities, Black MSM in the South. First, to understand predictors of STIs, she will explore the relationship between social factors (e.g. social isolation) and STI incidence; these relationships will inform research efforts to focus on those at highest risk for STIs. Second, she will investigate facilitators and barriers to STI risk reduction practices through in-depth interviews (IDIs) with Black MSM PrEP users. She will specifically inquire about peer support as a facilitator to STI risk reduction practices, and gather initial feedback on the peer support features of the mSMART application (?app?). Data will be used to adapt the app, which will be further assessed in focus groups. These qualitative studies will give valuable insight into factors driving sexual risk taking that the mSMART app will then target. Third, in a pilot investigation of Black MSM PrEP users with predictive STI risk factors, as identified in the first aim, she will conduct a randomized study to determine the feasibility and preliminary impact of the adapted mSMART app in reducing STI incidence. Through this proposal, Dr. Clement will build upon her experience in STIs with continued pursuit of critical public health research, and as a result be prepared to become a national leader in the field of HIV/STI prevention. Didactic coursework will bolster Dr. Clement's quantitative analytic skills and solidify her knowledge base. Additionally, she will gain training and experience in mHealth technology, a growing field with broad applications for health care access and delivery. She will also gain an appreciation for the application of qualitative science that will serve fruitful in future investigations. The mentorship team, led by Dr. Susanna Naggie, an experienced HIV investigator, will include experts in behavioral science related to PrEP (Dr. Amy Corneli), the use of mHealth technology in Black MSM (Dr. Sara LeGrand), and biostatistics (Dr. Cliburn Chan). Also included as collaborators are Dr. Arlene Sea, an expert in STIs who is Medical Director of the Durham County Department of Public Health, Dr. Mehri McKellar, the Medical Director of the Duke PrEP clinic, Dr. John Mitchell, a clinical psychologist who has pioneered the mobile app mSMART in PrEP users, Dr. Lisa Hightow-Weidman, a recognized leader in the field of technology based interventions aimed at HIV/STI prevention in young MSM, and Dr. Kenneth Mayer, a world expert in biomedical HIV prevention and the intersection of STIs and PrEP. The proposed aims and accompanying training plan will allow Dr. Clement to mature into an independent researcher in HIV/STI prevention and provide a basis for an R01 to implement her mobile technology intervention for STI prevention in Black MSM PrEP users.